Such angle-measurement systems may be used to measure rotary motions or rotational positions of a machine part, such as a shaft, on which a body having angle scaling is affixed in a torsionally fixed manner. The angle scaling may have, for example, an optical or magnetic graduation which may be scanned accordingly. The rotary motion is recorded either incrementally or absolutely. The output measured value is, for example, a sequence of counting pulses, a counter value or a code word. Corresponding angle-measurement systems may be used in so-called pick-and-place machines in the manufacture of electronic components, or in machine tools for the measuring of rotary movements. The reproducibility or repeatability of the measurement of rotational angles of machine parts down to precisely only a few angular seconds is considered to be important when working with the extremely dynamic pick-and-place machines, for example. In particular, the absolute accuracy of the measuring results of an angle-measurement system is considered to be crucial for machine tools. Angle-measurement systems are often designed such that they have no separate mounting of the components that are rotatable relative to each other.
The precision of an angle measurement is influenced to a considerable extent by the quality of the angle scaling, the contouring accuracy of the body bearing the angle scaling and by the deviation in the radial eccentricity of the mounting. Also considered to be important in this context is that the smallest possible eccentricity of the body with respect to the mounting is achieved. Furthermore, in particular in applications involving high dynamics, such bodies should be joined to the corresponding machine part in an extremely rigid manner and, in addition, the body itself should be designed as a rotationally or torsionally stiff body, if possible, to allow precise measuring results to be achieved.
In the brochure entitled “Angle Measuring Devices” of HEIDENHAIN of February 2004, an installable angle measuring device (type ERA or ERM) which has a graduation drum arranged as monolithic body is illustrated on page 23. An inner annular region of this graduation drum has a flange-type arrangement for connection to a shaft.
Conventional devices are believed to have certain disadvantages, such as that relatively high demands may need to be placed on the mounting surface, for example, on the front face of a shaft and/or clamping surface of the body, in order for the measuring results or the measuring signals not to deteriorate.